Delegation of a Joystick
Video production switchers are capable of generating many effects and require a large number of parameters to be set and modified by the operator. A multi-axis joystick is a convenient way of adjusting these parameters. Traditionally the control panel surface of a video switcher has an area dedicated to the joystick and contains a large number of buttons and lamps. The buttons are used to delegate the joystick to control a single particular function. The lamps light to indicate which function is being controlled by the joystick.
Multiple functions may be delegated simultaneously by selecting multiple buttons. These multiple buttons may then illuminate simultaneously to indicate the functions being simultaneously controlled by the joystick. For a modern switcher with a large number of controllable items, an equally large number of buttons and lamps are required.
This approach has many drawbacks. A large amount of panel real estate is wasted in providing a button for each controllable function. It becomes impractical to provide a button for each function on the switcher that can be controlled by the joystick. This leads to buttons that serve dual purposes or functions that cannot be easily selected for control. Secondly, in live production situations where speed and accuracy of operation is critical, it can be difficult for the operator to quickly assess which function is being controlled by trying to identify a lit button or buttons in a large grouping of buttons. Dual-purpose buttons or functions without dedicated buttons complicate the matter and make it difficult to operate the joystick with certainty of which parts or characteristics of a video scene will be modified.
Identification of Button Groups on a Panel
On a control surface with a multitude of buttons and indicators, such as a production switcher panel, it is desirable to allow an operator to easily identify buttons and to logically group buttons having related functions, and do so quickly. This has been done using several methods.
Firstly, physical locations of buttons and button groups can delineate different functional areas of a control panel. For example, buttons for “keyer control” can be grouped together, and buttons for “memory” could be grouped in a separate area. This has the disadvantage that once the control panel has been designed, the groupings are fixed and do not allow for future functionality enhancement.
Colored button caps have also been used to delineate groups of related functions. This has similar disadvantages in that the colors are fixed and cannot be quickly changed. Additionally, the color choices are limited to those made by the manufacturer of the control panel and may not be aesthetically pleasing to the end user.
Another method to aid in the identification of buttons in a dark environment, such as a television control room, is the use of button illumination, using one or more light sources per button. This illumination may be used to highlight active functions or as an overall backlight to improve readability of button legends. Some implementations allow adjustment of button light source(s) brightness. This illumination is typically limited to one color, or a small number of color choices as dictated by the capabilities of the buttons' light source(s) and indicators installed on the control panel. This, disadvantageously, is limited to the color choices set out by the manufacturer and may not be aesthetically pleasing to the end user. It can also increase costs, because of the circuitry needed to drive each indicator independently.
Color Uniformity
Lighted indicators, such as Light Emitting Diodes (LEDs), are subject to variation by the nature of their manufacture. This can result in the unpleasant effect of low color uniformity, due not only to technological limitations of currently available light sources, but also to the sensitivity of human vision to detect subtle color differences, when many light sources with a similar but imperfectly matched color are lit, side-by-side. Using tighter color tolerance light sources is not a feasible option in many implementations, due to their higher cost and inherent limitations.
Uniform color and brightness of lighted indicators can also be significant for proper operation of a control panel. For example, a green indicator could indicate “All OK”, whereas a yellow indicator might indicate “Caution”. If the indicators are improperly calibrated, it is possible that an indicator which the panel had driven to be lit as green would actually appear yellow, resulting in an operator misinterpreting the indicator and not taking an appropriate action.
Control of Indicator Brightness Using Pulse-Width Modulation (PWM)
One common method of controlling the brightness of light sources such as LEDs is through the use of PWM, which is commonly known in the electronics industry. This method cycles the voltage or current feeding a light source ON and OFF rapidly to simplify the driver circuits. By varying the relative time the voltage or current is ON versus OFF, the human eye perception of brightness may be controlled. For example, a light source that is ON 100% of the time will appear to the human eye to be brighter than a light source that toggles quickly enough, and is ON for 50% of the time and OFF the other 50%.
Existing methods to generate PWM produce a waveform with a continuous ON time, and minimum transitions per cycle. Once a light source is turned ON, a monotonic digital counter will turn it OFF at a pre-programmed point in time during the cycle. This allows the perceived brightness of the light source to be varied by manipulating the amount of “ON time” versus “OFF time”.
One disadvantage of this scheme is the PWM frequency has to be quite high (more than 200 Hz) to prevent discomfort to the human eye (a subtle “flicker”, particularly noticeable when many light sources located sided by side are turned ON and OFF at the same time). One approach to reduce this effect is to increase the refresh frequency, but this makes the control and power circuitry more complex and expensive. Another option trades off refresh frequency for PWM resolution (the minimum ON time change possible, given the size and increment step of the counter).
Identification of Key Types
One of the primary features of a switcher is called a keyer. A keyer layers one piece of video, called a key, on top of another. A good example of this is the placement of the name of a newscaster on top of live video of that newscaster. There are several different types of keys, including linear, luminance, auto select, chroma, Preset Pattern, and Over The Shoulder (OTS) boxes, for example. The operator of a switcher panel or switcher chooses which type of key is to be used. The operator may have many keys available for use simultaneously, often more than 12. It is very important for the operator to be able to quickly verify that the correct key type has been selected on every keyer.
Switchers have one button per key type selectable on the control panel for a selected keyer. One and only one of these buttons will be lit at any time showing the currently selected key type. Pressing another key type button changes the key type to the new selection and lights that button.
Given a large panel with many keys and many key types, it is both space and cost prohibitive to provide one button per keyer per type. For example, a switcher with 12 keyers that each support 5 key types would require 60 buttons in this configuration. Switchers often place one set of key type buttons beside a set of buttons to select the keyer to modify. This reduces the number of buttons required but only allows the user to see the key type state for one keyer at a time. Verifying that all key types are correct would require 12 button presses in the case of a 12 keyer switcher.
Graphic Display
Almost all switchers have a large graphical display to assist the operator in using the product. These displays provide access to menus, one at a time, that show the state of controls as well as allowing the user to change these values. Since switchers are often used in a very fast live environment, every second counts for an operator. A menu that is currently being displayed on a switcher is chosen in one of two ways. A menu might be explicitly chosen by the user, sometimes through several button presses for navigating a menu tree. Alternatively, by pressing certain buttons on the main control panel surface, a user may cause, as a secondary effect from the button being pressed, the display to load a particular menu.
Fixed Panel Layout
Traditional switcher panels tend to be designed without flexibility in mind. Once the product is available to the customers, the form-fit of the control panel is fixed. If a customer wants the arrangement to be slightly different, the entire panel will have to be re-designed.